Disruptive behavior disorders are characterized by antisocial, aggressive behaviors. Externalizing problems are the most commonly diagnosed mental health problems of childhood. They tend to be stable over time, resistant to treatment, and linked to psychiatric disorders in adolescence and adulthood. Early onset aggression is a precursor of life-course persistent antisocial behavior. Little is known, however, about constitutional and environmental factors, and their interactions, that contribute to different developmental outcomes. Eighty-two 4-5 year-old children at low, moderate or high risk for later disruptive behavior disorders (based on initial levels of externalizing problems), have been studied at three subsequent time points; 6-7, 8-10, and 12-13 years. Social, emotional, cognitive, and physiological areas of child functioning are examined, in conjunction with socialization experiences. The goal is to identify key factors that contribute to continuity and change over time in young children's behavioral problems. Child and parent risk and protective factors that contribute to continuity versus amelioration of problems during middle childhood have been identified. Current projects focus on the functioning of these children in early adolescence. Main findings of five projects are summarized below.(1) Symptoms of Attention Deficit Hyperactivity Disorder show consistency across contexts, informants and measures. ADHD symptoms in adolescence are predicted by earlier impairments in cognitive functioning, hostility and low guilt. Symptoms of subtypes of ADHD are associated with different cognitive and emotional profiles. (2) By adolescence, there are important gender differences in males and females who were aggressive in early childhood. Girls are more likely than boys to develop comorbid symptoms of depression and anxiety. The development of comorbid internalizing problems may serve to inhibit later antisocial behavior but create risk for subsequent mood disorders. (3) Preschool children who had difficulty processing nonverbal emotion cues have more behavior problems and less self-competence in adolescence. These longitudinal patterns are stronger for boys than girls. (4) Male adolescents with the most severe behavior problems at preschool age have higher cortisol levels than less disturbed children during and following social challenge paradigms that involve discussions of conflict. Dysregulated physiological reactivity in children with histories of aggression and antisocial behavior thus may contribute to maladaptive behaviors and disruptiveness, particularly in boys. (5)Early socialization processes contribute to later emotional and behavioral problems. Early marital conflict predicts both internalizing and externalizing problems in adolescence, even after these symptoms in early childhood have been taken into account. In addition, early supportive parenting predicted adolescent experience and control of anger suggesting ways in which positive parenting may help children manage their hostile impulses. Cumulatively, these studies highlight the need to study the interaction of biological and environmental processes to understand the different developmental trajectories of young boys and girls with conduct problems.